U.S. Pat. No. 5,030,600 of George T. Hida et al. discloses a composite material containing at least 70 weight percent of single-phase beta sialon and at least 20 weight percent of alpha-alumina. Although the composite material of this patent has excellent mechanical and thermal properties, its properties are not good enough for use in severe environments requiring a particular combination of excellent thermal and excellent mechanical properties.
It is an object of this invention to provide a sialon material which a hardness at least 19 GigaPascals, a strength of at 1,000 megaPascals (at room temperature), a fracture toughness of at least 6 megaPascals, and a strength decay at 1,350 degrees Celsius of less than 25 percent.